1. Field of the Invention
The present invention relates to a compressor, and in particular, to the arrangement of a pressure-regulating valve in an oil separator mounted on a compressor main body.
2. Description of the Related Art
A compressor, which compresses gas such as refrigerant gas to circulate the gas in an air-conditioning system, is conventionally used in an air-conditioning system.
The compressor includes a main body which is housed in a housing and compresses gas by rotary driving, and a discharge section to which high-pressure gas is ejected from the main body. The compressor is configured to discharge the high-pressure gas outside the housing from the discharge section.
The compressor main body includes an oil separator which separates oil from the high-pressure gas ejected from the compressor main body. The oil separated by the oil separator is accumulated in the bottom of the discharge section.
The oil accumulated in the bottom of the discharge section is guided to the compressor main body by the pressure (pressure of high-pressure gas) in the discharge section.
The compressor main body includes a rotation shaft rotating by an applied rotary driving force, a cylindrical rotor rotating integrally with the rotation shaft, a cylinder arranged outside the outer circumferential face of the rotor, and including an inner circumferential face having an approximately ellipsoidal shape in section, two side blocks which cover both end faces of the cylinder and the rotor, and a plurality of plate-like vanes buried in the rotor at equal angular intervals about the rotation shaft. Each of the vanes is projectable from the outer circumferential face of the rotor by back-pressure. The projection amount changes according to the rotation of the rotor while the projected leading ends of the vanes have contact with the inner circumferential face of the cylinder.
Compression rooms are formed by the rotor, cylinder, both side blocks and two vanes in tandem in the rotation direction of the rotor. Gas is sucked in each compression room, then is compressed, and is ejected to the discharge section as high-pressure gas due to the change in the volume of each compression room according to the rotation of the rotor.
The projection force of the vane is too strong if the vane receives high back-pressure although the back-pressure is oil guided to the compressor main body. This causes excessively strong contact between the leading end of the vane and the inner circumferential face of the cylinder. For this reason, a limiter, which limits the pressure of the guided oil to an intermediate pressure lower than the pressure in the discharge section, is provided in the compressor main body. The oil limited to the intermediate pressure is supplied to an oil path and a vane back-pressure space.
In addition, the projection force of the vane is increased not only by the back-pressure that the vane receives but also a centrifugal force generated by the rotation of the rotor.
In this case, the vanes follow the inner circumferential face of the cylinder by the above-described operation during the normal rotation of the compressor. However, the inner pressure in the discharge section is lowered if the compressor is maintained in a resting state, and the back-pressure of the vanes is also lowered. For this reason, the leading ends of some vanes are separated from the inner circumferential face of the cylinder due to their own weights, and thus, some compression rooms are not formed.
If the compressor starts up in such a state, the back-pressure is small just after the start of the rotation of the rotor. Thus, it may take a long time to obtain constant high-pressure gas because the vanes do not instantly project.
The leading ends of the vanes are separated from the inner circumferential face of the cylinder due to the pressure of the compression rooms acting on the leading ends of the vanes pressed against the inner circumferential face of the cylinder if the back-pressure of the vanes is not increased to a certain degree. This may cause chattering.
Therefore, Japanese Patent Application Publication No. 2008-223526 proposes to create a high-pressure bypass from a vane back-pressure space to a discharge section in an oil separator, and to provide in the high-pressure bypass a pressure-regulating valve which opens the bypass until the pressure (static pressure) in the discharge section reaches predetermined pressure and closes the bypass after the pressure (static pressure) in the discharge section reaches the predetermined pressure as a mechanism for improving the projection performance of the vanes just after the start-up of the compressor.
In this compressor, the pressure-regulating valve opens the high-pressure bypass just after the startup of the compressor. With this configuration, the inner pressure in the discharge section directly acts on the oil path without the limiter, and the back-pressure of the vanes is increased so as to be higher than the pressure through the limiter, so that the projection performance of the vanes can be improved.
The oil separator includes a centrifugal-type oil separator which centrifugally separates oil by a force when compressed gas is ejected from the compressor main body. This oil separator includes an inside space surrounded by an inner circumferential wall face which centrifugally separates oil by a force when compressed gas is ejected from the compressor main body, and a bottom wall face in which the centrifugally-separated oil falls. The centrifugally-separated oil in the inside space is discharged to the lower portion of the discharge section from an oil discharge hole formed in the bottom wall face.
The pressure-regulating valve provided in the oil separator may be affected by dynamic pressure because the jet flow (dynamic pressure) of the gas ejected from the oil separator is strong. The pressure-regulating valve closes the bypass due to the impact of the dynamic pressure even if the pressure (static pressure) in the discharge section does not reach predetermined pressure.
Therefore, the pressure value of the pressure-regulating valve should be set in accordance with the strength of the jet flow (dynamic pressure) of the gas ejected from the oil separator. However, making such a setting is difficult in practice because the strength of the jet flow changes according to the rotation number and the pressure of the compressor.